What is the definition of tubular secretion?

Correct Answer: B

Rationale: Tubular secretion is the selective transfer from peritubular capillaries to the tubular lumen removes waste (e.g., H , drugs) into urine. Lumen-to-capillary is reabsorption opposite. Reabsorption conserves e.g., glucose. Filtration occurs at glomerulus not tubular. Selective capillary-to-lumen movement distinguishes it, critical for excretion, unlike reabsorption or filtration processes.

Correct Answer: C

Rationale: Intercalated cells maintain acid-base balance secrete H or HCO₃⁻ in the collecting duct (e.g., pH regulation). Juxtaglomerular cells release renin pressure control. Principal cells manage water/Na ADH/aldosterone. Macula densa senses NaCl GFR feedback. Acid-base role distinguishes intercalated cells, critical for homeostasis, unlike pressure, water, or sensing cells.

Correct Answer: B

Rationale: Principal cells are in connecting tubules (distal/collecting) manage water/Na (e.g., ADH/aldosterone). Intercalated disc is cardiac not renal. Macula densa is distal sensing, not typical connecting. Juxtaglomerular cells are arteriolar renin-focused. Principal cells' presence distinguishes them, key to tubular regulation, unlike misnamed or adjacent cells.

Correct Answer: A

Rationale: Glucose appears before Tmax due to nephron variation heterogeneous Tmax (e.g., some saturate early). Complete reabsorption holds below Tmax false here. Passive reabsorption isn't glucose active. Secretion doesn't apply glucose isn't secreted. Variation distinguishes it, key to splay phenomenon, unlike total or mechanism errors.

Correct Answer: B

Rationale: Sodium entering the tubule at the luminal membrane is false enters cell from lumen, exits to blood (e.g., PCT). Early reabsorption is true ~65%. Na /K -ATPase drives active exit passive misstated but mechanism holds. All correct overstates entry error. Direction distinguishes the falsehood, key to Na transport, unlike location or pump truths.